In recent years, large-size screens have been often used for image display, in various places such as disaster-prevention headquarters, monitor rooms of power stations, and sites of concerts and of events. In typical cases, a so-called multidisplay apparatus that allows a plurality of image display apparatuses to display a plurality of images side by side on a large screen is used (hereinafter, each projection image display apparatus is referred to as “a projector”).
In such a multidisplay apparatus, continuity of the projection pictures is important so that viewers do not feel a sense of inconsistency between the displayed images. Conventional projectors have a function for adjusting the brightness of their projection pictures, and so can equalize the brightness between the pictures, thereby maintaining continuity of the adjacent pictures.
Conventional lamps used for such projectors are high intensity lamps such as high-pressure mercury lamps and xenon lamps. Such high intensity lamps have a certain operating life, and their brightness is characterized by decreasing rapidly within a certain period in the lighting start, and then moving on to gradual decrease afterwards.
Accordingly, the conventional lamps have the following problem. Suppose that the lamp for one of the projectors is replaced, and the brightness of the projector is adjusted to be the same as those of the other projectors. Even so, as the time elapses, the brightness of the projector will get out of sync with the brightness of the other projectors.
Conventionally, adjusters have to perform regular brightness adjustment (e.g. in every 200 hours of lighting for a lamp), so as to correct the difference in brightness generated between the plurality of projectors incident to elapse of time. However it is a troublesome work. Besides, the adjusters are usually specialists in that field, which incurs a great amount of maintenance cost.
The present invention is conceived in light of the aforementioned problem, and has an object of providing: an image display apparatus for realizing image display with integrity on the whole, which hardly necessitates adjustment by specialists; a multidisplay apparatus equipped with a plurality of such image display apparatuses; and a brightness management apparatus that manages the brightness of each image display apparatus in the multidisplay apparatus.